Find the part with the fewest good answers and the greatest effect on everything else.
That is the center.
It might be the first action, the data model, the trust moment, the permission boundary, the feedback loop, the handoff, the interface metaphor, or the final artifact.
Shape that first.
Do not let AI build the easy outer parts while the center remains unresolved.
The right amount of newness in that center makes a better thing feel newly obvious.